Organic light emitting diode display substrate, manufacturing method thereof, and display device

ABSTRACT

An organic light emitting diode display substrate includes a light emitting unit layer, a first band gap layer and a color conversion layer. The first band gap layer and the color conversion layer are on a light exit path of the light emitting unit layer. The light emitting unit layer includes first, second and third light emitting units periodically arranged on a driving substrate and emitting light of a first color. The color conversion layer converts a part of the light of the first color into light of a second color and a third color. The first band gap layer is between the light emitting unit layer and the color conversion layer. The first band gap layer transmits the light of the first color in a light exit direction, and reflects the light of the second color and the light of the third color.

RELATED APPLICATIONS

The present application claims the benefit of Chinese Patent ApplicationNo. 201811443609.0, filed on Nov. 29, 2018, the entire disclosures ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the field of display technology, andin particular to an organic light emitting diode display substrate, amanufacturing method thereof, and a display device.

BACKGROUND

Organic light emitting diode (OLED) is an active light emitting displaydevice, which has the advantages of self-luminescence, wide viewingangle, high contrast, low power consumption, and extremely high responsespeed. At present, for small-size OLED products, the organicelectroluminescent layer is usually formed by a vapor depositionprocess, and the modulation effect of the optical resonator is used toachieve low power consumption and high color gamut. However, due to theexpensive preparation materials and the need for fine metal mask (FMM)in the preparation process, this preparation method cannot achievestable mass production of large-size OLED products.

Mass-produced large-size OLED products mainly use the structureincluding white light OLEDs and color filters, but this structure hasthe problems of large power consumption and insufficient color gamut. Inorder to solve the problems of power consumption and color gamut, therelated art proposes a structure including a blue OLED, a green quantumdot color conversion layer, and a red quantum dot color conversionlayer. The inventors of the present application have found that thisstructure not only has the problem of insufficient green and red lightoutput, but also has the problem of a large amount of blue light ingreen and red light, resulting in poor color purity of the product.

SUMMARY

An embodiment of the present disclosure provides an organic lightemitting diode display substrate. The organic light emitting diodedisplay substrate includes a light emitting unit layer, a first band gaplayer and a color conversion layer. The first band gap layer and thecolor conversion layer are disposed on a light exit path of the lightemitting unit layer; the light emitting unit layer includes a firstlight emitting unit, a second light emitting unit, and a third lightemitting unit periodically arranged on a driving substrate and emittinglight of a first color; the color conversion layer is configured toconvert a part of the light of the first color into light of a secondcolor and light of a third color, respectively; the first band gap layeris disposed between the light emitting unit layer and the colorconversion layer and covers the second light emitting unit and the thirdlight emitting unit; the first band gap layer is configured to transmitthe light of the first color in a light exit direction, and reflect thelight of the second color and the light of the third color.

Optionally, the color conversion layer includes a second colorconversion unit disposed on a light exit path of the second lightemitting unit and converting the light of the first color into the lightof the second color, and a third color conversion unit disposed on alight exit path of the third light emitting unit and converting thelight of the first color into the light of the third color.

Optionally, the first band gap layer further covers the first lightemitting unit.

Optionally, the organic light emitting diode display substrate furtherincludes a color filter layer disposed on a light exit path of thesecond color conversion unit and the third color conversion unit. Thecolor filter layer is configured to transmit the light of the secondcolor and the light of the third color in the light exit direction andabsorb the light of the first color.

Optionally, the color filter layer includes a second filter unit and athird filter unit; the second filter unit corresponds to a position ofthe second color conversion unit, and is configured to transmit thelight of the second color in the light exit direction and absorb thelight of the first color; the third filter unit corresponds to aposition of the third color conversion unit, and is configured totransmit the light of the third color in the light exit direction andabsorb the light of the first color.

Optionally, the first band gap layer has a transmittance of ≥80% for thelight of the first color, and has a reflectivity of ≥85% for the lightof the second color and the light of the third color.

Optionally, the organic light emitting diode display substrate furtherincludes: a second band gap layer disposed on a light exit path of thesecond color conversion unit and the third color conversion unit. Thesecond band gap layer is configured to transmit the light of the secondcolor and the light of the third color in the light exit direction andreflect the light of the first color in a direction opposite to thelight exit direction.

Optionally, the second band gap layer is disposed on a planarizationlayer covering the second color conversion unit and the third colorconversion unit, and includes a second band gap unit and a third bandgap unit; the second band gap unit corresponds to a position of thesecond color conversion unit, and is configured to transmit the light ofthe second color in the light exit direction and reflect the light ofthe first color in a direction opposite to the light exit direction; thethird band gap unit corresponds to a position of the third colorconversion unit, and is configured to transmit the light of the thirdcolor in the light exit direction and reflect the light of the firstcolor in the direction opposite to the light exit direction.

Optionally, the second band gap unit has a transmittance of ≥80% for thelight of the second color and a reflectivity of ≥85% for the light ofthe first color; the third band gap unit has a transmittance of ≥80% forthe light of the third color and a reflectivity of ≥85% for the light ofthe first color.

Optionally, each of the first band gap layer and the second band gaplayer is one of a photonic band gap layer and a stacked structure layer;a thickness of the photonic band gap layer is 0.5 μm to 2.0 μm; athickness of the stacked structure layer is 0.5 μm to 10.0 μm, thestacked structure layer includes 3 to 5 sequentially stacked dielectriclayers, and the refractive indexes of adjacent dielectric layers aredifferent from each other.

Optionally, the light of the first color is blue light, and the colorconversion layer is a quantum dot conversion layer.

An embodiment of the present disclosure further provides an organiclight emitting diode display substrate. The organic light emitting diodedisplay substrate includes a light emitting unit layer, a colorconversion layer and a second band gap layer. The color conversion layerand the second band gap layer are disposed on a light exit path of thelight emitting unit layer; the light emitting unit layer includes afirst light emitting unit, a second light emitting unit, and a thirdlight emitting unit periodically arranged on a driving substrate andemitting light of a first color; the color conversion layer isconfigured to convert a part of the light of the first color into lightof a second color and light of a third color, respectively; the secondband gap layer is disposed on a side of the color conversion layer awayfrom the light emitting unit layer; the second band gap layer isconfigured to transmit the light of the second color and the light ofthe third color in a light exit direction, and reflect the light of thefirst color in a direction opposite to the light exit direction.

Optionally, the color conversion layer includes a second colorconversion unit disposed on a light exit path of the second lightemitting unit and converting the light of the first color into the lightof the second color, and a third color conversion unit disposed on alight exit path of the third light emitting unit and converting thelight of the first color into the light of the third color.

Optionally, the second band gap layer is disposed on a planarizationlayer covering the second color conversion unit and the third colorconversion unit, and includes a second band gap unit and a third bandgap unit; the second band gap unit corresponds to a position of thesecond color conversion unit, and is configured to transmit the light ofthe second color in the light exit direction and reflect the light ofthe first color in a direction opposite to the light exit direction; thethird band gap unit corresponds to a position of the third colorconversion unit, and is configured to transmit the light of the thirdcolor in the light exit direction and reflect the light of the firstcolor in the direction opposite to the light exit direction; the secondband gap unit has a transmittance of ≥80% for the light of the secondcolor and a reflectivity of ≥85% for the light of the first color; thethird band gap unit has a transmittance of ≥80% for the light of thethird color and a reflectivity of ≥85% for the light of the first color.

Optionally, the second band gap layer is one of a photonic band gaplayer and a stacked structure layer; a thickness of the photonic bandgap layer is 0.5 μm to 2.0 μm; a thickness of the stacked structurelayer is 0.5 μm to 10.0 μm, the stacked structure layer includes 3 to 5sequentially stacked dielectric layers, and the refractive indexes ofadjacent dielectric layers are different from each other.

Optionally, the light of the first color is blue light, and the colorconversion layer is a quantum dot conversion layer.

An embodiment of the present disclosure also provides a display deviceincluding the organic light emitting diode display substrate asdescribed above.

An embodiment of the present disclosure further provides a method formanufacturing an organic light emitting diode display substrate. Themethod includes: forming a light emitting unit layer that emits light ofa first color, the light emitting unit layer including a first lightemitting unit, a second light emitting unit, and a third light emittingunit periodically arranged on a driving substrate; and forming a firstband gap layer and a color conversion layer, the first band gap layerbeing between the light emitting unit layer and the color conversionlayer, the color conversion layer being configured to convert a part ofthe light of the first color into light of a second color and light of athird color, respectively; the first band gap layer being configured totransmit the light of the first color in a light exit direction, andreflect the light of the second color and the light of the third color.

Optionally, the method further includes: forming a second band gaplayer, the second band gap layer being on a side of the color conversionlayer away from the light emitting unit layer, and the second band gaplayer being configured to transmit the light of the second color and thelight of the third color in the light exit direction and reflect thelight of the first color in a direction opposite to the light exitdirection.

An embodiment of the present disclosure further provides a method formanufacturing an organic light emitting diode display substrate. Themethod includes: forming a light emitting unit layer that emits light ofa first color, the light emitting unit layer including a first lightemitting unit, a second light emitting unit, and a third light emittingunit periodically arranged on a driving substrate; and forming a colorconversion layer and a second band gap layer, the second band gap layerbeing on a side of the color conversion layer away from the lightemitting unit layer, and the second band gap layer being configured totransmit the light of the second color and the light of the third colorin a light exit direction and reflect the light of the first color in adirection opposite to the light exit direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are used to provide a further understanding of thetechnical solutions of the present disclosure, constitute a part of thespecification, and are used to explain the technical solutions of thepresent disclosure together with the embodiments of the presentdisclosure, and do not constitute limitations on the technical solutionsof the present disclosure. The shapes and sizes of the components in thedrawings do not reflect the true scale, and the purpose is only toillustrate the present disclosure.

FIG. 1a is a schematic structural diagram of an embodiment of an OLEDdisplay substrate provided by the present disclosure;

FIG. 1b is a schematic structural diagram of another embodiment of anOLED display substrate provided by the present disclosure;

FIG. 1c is a schematic top view of the OLED display substrate shown inFIG. 1 b;

FIG. 2 is a schematic structural diagram of a light emitting unit of theembodiment shown in FIG. 1 provided by the present disclosure;

FIG. 3a and FIG. 3b are schematic structural diagrams of the first bandgap layer of the embodiment shown in FIG. 1 provided by the presentdisclosure;

FIG. 4 is a working principle diagram of the first band gap layer of theembodiment shown in FIG. 1 provided by the present disclosure;

FIG. 5 is a schematic structural diagram of another embodiment of anOLED display substrate provided by the present disclosure;

FIG. 6 is a schematic structural diagram of yet another embodiment of anOLED display substrate provided by the present disclosure;

FIG. 7 is a working principle diagram of the second band gap layer ofthe embodiment shown in FIG. 6 provided by the present disclosure;

FIG. 8a , FIG. 8b , and FIG. 8c are spectrum diagrams of the embodimentshown in FIG. 6 provided by the present disclosure; and

FIG. 9 is a schematic structural diagram of still another embodiment ofan OLED display substrate provided by the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

The implementation of the present disclosure will be described below inmore detail in combination with the drawings and the embodiments. Thefollowing embodiments are used for explanation of the presentdisclosure, not for limitation of the scope of the present disclosure.It should be noted that the embodiments in the present disclosure andthe features in the embodiments can be arbitrarily combined with eachother without conflict.

The inventors of the present application have found that in the solutionincluding blue light OLED, green quantum dot color conversion layer, andred quantum dot color conversion layer proposed by the related art,green light is the light converted by the green quantum dot colorconversion layer absorbing blue light, and red light is the lightconverted by the red quantum dot color conversion layer absorbing bluelight. The green light emitted from the green sub-pixel and the redlight emitted from the red sub-pixel conform to the traditionalLambertian. The Lambertian refers to that the incident light isreflected uniformly in all directions, that is, the incident light iscentered on the incident point and reflected isotropically around theentire hemispherical space, which is called diffuse reflection, orisotropic reflection. Due to the characteristics of color conversion ofquantum dots, part of the converted green and red light does not exitfrom the light exit surface, thus resulting in insufficient green andred light output. Insufficient green and red light output leads toincreased power consumption of the product, because in order to improvethe brightness of green and red light, the output of the light emittingunit needs to be increased. In addition, due to the limited absorptionefficiency of quantum dot materials, and the absorption efficiency isgreatly affected by the concentration, it is impossible to completelyconvert blue light, so green light and red light inevitably contain bluelight, resulting in insufficient color purity of green light and redlight, which in turn leads to insufficient product color purity.

In view of the problem of insufficient color purity of the existingsolution including blue light OLED, green quantum dot color conversionlayer and red quantum dot color conversion layer, the embodiments of thepresent disclosure provide an OLED display substrate, a manufacturingmethod thereof, and a display device.

The main structure of the OLED display substrate of the embodimentprovided by the present disclosure includes a light emitting unit layer,a band gap layer, and a color conversion layer. The light emitting unitlayer emits light of a first color. The band gap layer and the colorconversion layer are disposed on the light exit path of the lightemitting unit layer. The color conversion layer is configured to converta part of the light of the first color into light of a second color andlight of a third color, respectively. The band gap layer is configuredto emit light of the second color and light of the third color to thelight exit direction of the organic light emitting diode displaysubstrate. The light exit direction of the organic light emitting diodedisplay substrate is consistent with the light exit direction of thelight emitting unit layer.

In particular, the light emitting unit layer includes a first lightemitting unit, a second light emitting unit, and a third light emittingunit periodically arranged on a driving substrate and emitting light ofthe first color. The color conversion layer includes: a second colorconversion unit disposed on a light exit path of the second lightemitting unit and converting the light of the first color into the lightof the second color, and a third color conversion unit disposed on alight exit path of the third light emitting unit and converting thelight of the first color into the light of the third color. The band gaplayer includes a first band gap layer and/or a second band gap layer.The first band gap layer is disposed between the light emitting unitlayer and the color conversion layer, and is configured to transmit thelight of the first color in the light exit direction and reflect thelight of the second color and the light of the third color in the lightexit direction. The second band gap layer is disposed on the light exitpaths of the second color conversion unit and the third color conversionunit, and is configured to transmit the light of the second color andthe light of the third color in the light exit direction and reflect thelight of the first color in a direction opposite to the light exitdirection.

The OLED display substrate provided by the present disclosureeffectively improves the light output efficiency and light output of thelight of the second color and the light of the third color by providinga band gap layer that increases the light output of the light of thesecond color and the light of the third color, and effectively improvesthe color purity of the product.

The technical solutions of the embodiments of the present disclosure aredescribed in detail below through specific embodiments.

FIG. 1a is a schematic structural diagram of an embodiment of an OLEDdisplay substrate provided by the present disclosure, in which the OLEDsare top-emitting OLEDs. As shown in FIG. 1a , the OLED display substrateof this embodiment includes: a driving substrate 10; a first lightemitting unit 21, a second light emitting unit 22, and a third lightemitting unit 23 periodically arranged on the driving substrate 10; thefirst light emitting unit 21, the second light emitting unit 22, and thethird light emitting unit 23 being capable of emitting light of thefirst color under the driving of the driving substrate 10; a first bandgap layer 30 disposed on the second light emitting unit 22 and the thirdlight emitting unit 23, the first band gap layer 30 being configured totransmit the light of the first color in a light exit direction, andreflect the light of the second color and the light of the third color;a second color conversion unit 42 and a third color conversion unit 43provided on the first band gap layer 30. The second color conversionunit 42 corresponds to the position of the second light emitting unit 22and is configured to convert the light of the first color emitted fromthe second light emitting unit 22 into light of the second color. Thethird color conversion unit 43 corresponds to the position of the thirdlight emitting unit 23 and is configured to convert the light of thefirst color emitted from the third light emitting unit 23 into light ofthe third color.

FIG. 1b is a schematic structural diagram of another embodiment of anOLED display substrate provided by the present disclosure. As shown inFIG. 1b , the first band gap layer 30 may cover the first light emittingunit 21, the second light emitting unit 22, and the third light emittingunit 23. The OLED display substrate may further be provided with a firstcolor conversion unit 41, and the first color conversion unit 41 isprovided on the first band gap layer 30 at a position corresponding tothe first light emitting unit 21. The first color conversion unit 41 istransparent (that is, the conversion rate is 0), and is configured totransmit blue light emitted from the first light emitting unit. FIG. 1cis a top view of the embodiment shown in FIG. 1b , and FIG. 1b is across-sectional view taken along line A-A in FIG. 1 c.

In this embodiment, the structure of the driving substrate 10 may be thesame as that of the related art, and includes several pixel unitsarranged in a matrix manner. Each pixel unit includes three sub-pixels.The three light emitting units are respectively disposed in the lightemitting regions formed by the pixel definition layer in the threesub-pixels. Each sub-pixel includes a thin film transistor driving thelight emitting unit to realize light emission. The thin film transistorincludes an active layer, a gate insulating layer, a gate electrode, aninterlayer insulating layer, a source electrode and a drain electrode,which will not be repeated here. FIG. 2 is a schematic structuraldiagram of the light emitting unit of the embodiment shown in FIGS. 1ato 1c . Each light emitting unit includes a first electrode 01, anorganic electroluminescent layer 02, and a second electrode 03. Theorganic electroluminescent layer 02 is provided between the firstelectrode 01 and the second electrode 03. The organic electroluminescentlayer 02 includes an organic light emitting layer, which can emit lightof the first color under the driving of the electric field between thefirst electrode and the second electrode. For the top emissionstructure, the first electrode is a reflective electrode, the secondelectrode is a transmissive electrode or a transflective electrode; forthe bottom emission structure, the first electrode is a transmissiveelectrode or a transflective electrode, and the second electrode is areflective electrode. In actual implementation, the organicelectroluminescent layer may include an electron transport layer and ahole transport layer in addition to the organic light emitting layer.Further, in order to improve the efficiency of injecting electrons andholes into the light emitting layer, the organic electroluminescentlayer may further include an electron injection layer disposed betweenthe cathode and the electron transport layer, and a hole injection layerprovided between the anode and the hole transport layer.

As shown in FIG. 2, since the three light emitting units all emit lightof the first color, the organic electroluminescent layer 02 of the threelight emitting units may have an integrated structure. The secondelectrode 03 of the three light emitting units may also have anintegrated structure. In this embodiment, an organic electroluminescentlayer with an integrated structure is provided. The organicelectroluminescent layer may be formed by an evaporation process withoutusing a mask, which does not require the use of FMM, reduces costs, andsimplifies the process.

In the above embodiment, the first band gap layer 30 has a transmittanceof ≥80% for the light of the first color and a reflectivity of ≥85% forthe light of the second color and the light of the third color.Optionally, the first band gap layer 30 has a transmittance of ≥90% forthe light of the first color. Optionally, the first band gap layer 30has a reflectivity of ≥95% for the light of the second color and thelight of the third color.

FIG. 3a and FIG. 3b are schematic structural diagrams of the first bandgap layer of the embodiments shown in FIGS. 1a-1c provided by thepresent disclosure. As shown in FIG. 3a , the first band gap layer 30 ofthis embodiment may be a photonic band gap (PBG) layer or anelectromagnetic band gap (EBG) layer, with a thickness of 0.5 μm to 2.0μm. The photonic band gap PBG is a periodic structure composed of aperiodic arrangement of a medium in another medium, also known as aphotonic crystal structure. The characteristic of the photonic band gapis that waves in a certain frequency range cannot propagate in itsperiodic structure, that is, there is a “forbidden band” in the photoniccrystal structure itself, so that light of a certain color can betransmitted and light of other colors can be reflected. In the same way,the electromagnetic band gap EBG is a periodically arranged arraystructure composed of a mixture of dielectric and metal, which hasobvious band stop characteristics and can control the propagation ofelectromagnetic waves. In actual implementation, the photonic band gaplayer or the electromagnetic band gap layer in this embodiment may beprepared in multiple ways by using one or more of the well-knowndielectric rod stacking, precision mechanical drilling, colloidalparticle self-organization growth, colloidal solution self-organizationgrowth, and semiconductor technology. The base material of the photonicband gap layer may be an inorganic material or an organic material. Whenan inorganic material is used as the base material, the inorganicmaterial can simultaneously serve as a protective layer for the threelight emitting units, blocking elements such as water and oxygen in theenvironment. When an organic material is used as the base material, aprotective layer may be additionally provided between the three lightemitting units and the photonic band gap layer, and the protective layerprovides protection for the three light emitting units.

The first band gap layer 30 of this embodiment may also be a stackedstructure layer forming a two-dimensional photonic crystal structure.The stacked structure layer includes a multi-layer structure in which aplurality of dielectric layers are sequentially stacked. The refractiveindexes of adjacent dielectric layers are different from each other. Themultiple dielectric layers with refractive index difference are used toachieve high transmission for the light of the first color and highreflectivity for the light of the second color and the light of thethird color. In actual implementation, any combination of inorganiclayers and/or organic layers may be used for the dielectric layer. Thematerial of the inorganic layer may be silicon nitride (SiN_(x)),silicon oxide (SiO₂), silicon carbide (SiC), sapphire (Al₂O₃), zincsulfide (ZnS), or zinc oxide (ZnO), which has water and oxygen barrierproperties, so that the inorganic layer can be used as the encapsulationlayer of the layer of the light emitting units. The material of theorganic layer may be polyvinyl pyrrolidone (PVP), polyvinyl alcohol(vinylalcohol polymer, PVA), 8-hydroxyquinoline aluminum (Alq),N,N′-diphenyl-N,N′-(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB) orHATCN, etc., so that the organic layer can also be used as a stressrelief layer. In this embodiment, the stacked structure has 3 to 5layers, with a thickness of 0.5 μm to 10.0 μm, and the refractive indexof the stacked structure material is 1.3 to 2.4. As shown in FIG. 3b ,the stacked structure layer includes a first inorganic layer 31, a firstorganic layer 32, and a second inorganic layer 33 stacked in sequence.In this structure, the first inorganic layer 31 is provided on the layerof the light emitting units and in contact with the three light emittingunits, and can simultaneously serve as a protective layer for the threelight emitting units, blocking elements such as water and oxygen in theenvironment. Of course, the stacked structure layer may also include anorganic layer, an inorganic layer and an organic layer stacked insequence. In this structure, a protective layer may be additionallyprovided between the three light emitting units and the organic layer,and the protective layer provides protection for the three lightemitting units. Further, the stacked structure layer may also includemultiple inorganic layers stacked in sequence. In actual implementation,the refractive index and thickness of each dielectric layer can bedesigned as required to achieve the characteristics of hightransmittance for the light of the first color and high reflectivity forthe light of the second color and the light of the third color.

In this embodiment, the color conversion layer may be a quantum dotconversion layer. Quantum dots (QDs), also known as nanocrystals, arenanoparticles composed of II-VI or III-V elements. The particle size ofquantum dots is generally between 1 and 20 nm. Due to the quantumconfinement of electrons and holes, the continuous energy band structurebecomes a discrete energy level structure with molecularcharacteristics, which can emit fluorescence after excitation. Theemission spectrum of quantum dots can be controlled by changing the sizeof the quantum dots. By changing the size of the quantum dots and theirchemical composition, their emission spectrum can cover the entirevisible light region. The material of quantum dots can be at least oneof zinc oxide, graphene, cadmium selenide (CdSe), cadmium sulfide (CdS),cadmium telluride (CdTe), zinc selenide (ZnSe), zinc telluride (ZnTe)and zinc sulfide (ZnS). Taking CdTe quantum dots as an example, when itsparticle size grows from 2.5 nm to 4.0 nm, the emission wavelength canbe shifted from 510 nm to 660 nm. In this embodiment, the second colorconversion unit 42 may be a transparent material layer doped withquantum dots of the second color. After the light of the first colorfrom the second light emitting unit 22 is incident on the second colorconversion unit 42, the quantum dots of the second color are excited bythe light of the first color and emit light of the second color,realizing the conversion of the light of the first color into the lightof the second color. The third color conversion unit 43 may be atransparent material layer doped with quantum dots of the third color.After the light of the first color from the third light emitting unit 23is incident on the third color conversion unit 43, the quantum dots ofthe third color are excited by the light of the first color and emitlight of the third color, realizing the conversion of the light of thefirst color into the light of the third color. In actual implementation,the second color conversion unit 42 and the third color conversion unit43 may also be quantum rods conversion layers, or other forms of lightcolor conversion materials. The conversion principle of the quantum rodconversion layer is similar to the quantum dot conversion layer, and thelight color conversion material may be cyanine dyes such as4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM-1),DCM-2, and DCJTB, 4,4-difluoro-1,3,5,7-tetraphenyl-4-bora-3a,4a-diaza-s-indacene, Lumogen red and Nile red etc. The quantum dotconversion layer, quantum rod conversion layer, or light colorconversion material used in this embodiment are all mature technologies,and their composition, structure, and preparation are well known tothose skilled in the art, which will not be repeated here.

In actual implementation, the light of the first color may be bluelight, green light or red light, the light of the second color may bedifferent from the light of the first color, and the light of the thirdcolor may be different from the light of the first color and the lightof the second color, which can be designed according to actual needs.Considering that the energy of blue light is higher than the energy ofred light and green light, it is easier to convert high-energy bluelight into low-energy green light or red light. Therefore, in theembodiment, the first light emitting unit 21, the second light emittingunit 22, and the third light emitting unit 23 are blue light emittingunits, that is, the light of the first color is blue light; the secondcolor conversion unit 42 is a conversion unit that converts blue lightinto green light, that is, the light of the second color is green light;the third color conversion unit 43 is a conversion unit that convertsblue light into red light, that is, the light of the third color is redlight.

FIG. 4 is a working principle diagram of the first band gap layer of theembodiment shown in FIG. 1 provided by the present disclosure. As shownin FIG. 4, the first light emitting unit 21, the second light emittingunit 22, and the third light emitting unit 23 emit blue light, which isrepresented by a solid line; the second color conversion unit 42converts the blue light into green light, and the green light isrepresented by a dot dash line; the third color conversion unit 43converts blue light into red light, and the red light is represented bya dotted line. Since the first band gap layer 30 has a hightransmittance for blue light, the blue light emitted by the first lightemitting unit 21, the second light emitting unit 22, and the third lightemitting unit 23 passes through the first band gap layer 30 and remainsblue light. After the blue light transmitted by the first band gap layer30 is incident on the second color conversion unit 42, the green quantumdots in the second color conversion unit 42 are excited by the bluelight to emit green light, and a part of the green light is emitted fromthe light exit surface of the second color conversion unit 42 (thesurface away from the surface of the first band gap layer 30), whileanother part of the green light exits from the light entrance surface ofthe second color conversion unit 42 (the surface adjacent to the firstband gap layer 30) and is incident on the first band gap layer 30. Sincethe first band gap layer 30 has a high reflectivity for green light, thegreen light entering the first band gap layer 30 is reflected back tothe second color conversion unit 42 and exits from the light exitsurface of the second color conversion unit 42. In this way, the firstband gap layer 30 reflects the green light, so that substantially allthe green light converted by the second color conversion unit 42 exitsfrom the light exit surface of the second color conversion unit 42,which effectively improves the green light output and the green lightoutput efficiency, increasing light brightness. Similarly, after theblue light transmitted by the first band gap layer 30 enters the thirdcolor conversion unit 43, the red quantum dots in the third colorconversion unit 43 are excited by blue light to emit red light, and apart of the red light is emitted from the light exit surface of thethird color conversion unit 43 (the surface away from the surface of thefirst band gap layer 30), while another part of the red light exits fromthe light entrance surface of the third color conversion unit 43 (thesurface adjacent to the first band gap layer 30) and is incident on thefirst band gap layer 30. Since the first band gap layer 30 has a highreflectivity for red light, the red light entering the first band gaplayer 30 is reflected back to the third color conversion unit 43 andexits from the light exit surface of the third color conversion unit 43.In this way, the first band gap layer 30 reflects the red light, so thatsubstantially all the red light converted by the third color conversionunit 43 exits from the light exit surface of the third color conversionunit 43, which effectively improves the red light output and the redlight output efficiency, increasing light brightness. In addition, ifthe red and green light output brightness of this embodiment is set tobe the same as the red and green light output brightness of the existingstructure, this embodiment can reduce the blue light emission of thesecond light emitting unit 22 and the third light emitting unit 23, andthus can effectively reduce power consumption.

Further, due to the limitation of the quantum dot material, after theblue light transmitted by the first band gap layer 30 is incident on thesecond color conversion unit 42 and the third color conversion unit 43,a small amount of blue light may not be converted into green light andred light. A part of this small amount of blue light may exit from thelight incident surfaces of the second color conversion unit 42 and thethird color conversion unit 43, and enter the first band gap layer 30.Since the first band gap layer 30 has a high transmittance for bluelight, this part of blue light is transmitted from the first band gaplayer 30 and does not return to the second color conversion unit 42 andthe third color conversion unit 43 anymore. In this way, due to thetransmission of blue light by the first band gap layer 30, the amount ofblue light in the green light and red light emitted by the second colorconversion unit 42 and the third color conversion unit 43 is reduced,thereby improving the color purity of green light and red light.

Although the embodiment has been described with top-emitting OLEDs, thesolution of this embodiment is also applicable to bottom-emitting OLEDsor double-sided emitting OLEDs. It can be seen from the abovedescription that the OLED display substrate of this embodiment can beadjusted in various ways. For example, according to actual needs, othertransparent layers may be provided between the light emitting unit layerand the first band gap layer, and between the first band gap layer andthe color conversion layer.

In this embodiment, the first band gap layer is provided between thelight emitting unit layer and the color conversion layer, the first bandgap layer transmits the light of the first color and reflects the lightof the second color and the light of the third color. Therefore, all thelight converted by the color conversion layer is emitted from thesub-pixels to the maximum extent, which effectively improves the lightoutput and the light output efficiency for the light of the second colorand the light of the third color, thereby improving the light outputbrightness. At the same time, the content of the light of the firstcolor in the light of the second color and the light of the third colordecreases, improving the color purity of the light of the second colorand the light of the third color, and improving the display quality.

FIG. 5 is a schematic structural diagram of another embodiment of anOLED display substrate provided by the present disclosure. Thisembodiment is an extension of the embodiment shown in FIG. 1b (since thefirst color conversion unit is optional, the first color conversion unit41 in FIG. 1b is omitted in FIG. 5). This embodiment is also providedwith a color filter layer. As shown in FIG. 5, the OLED displaysubstrate of this embodiment includes: a driving substrate 10; a firstlight emitting unit 21, a second light emitting unit 22, and a thirdlight emitting unit 23 arranged periodically on the driving substrate10; the light emitting unit 21, the second light emitting unit 22, andthe third light emitting unit 23 being capable of emitting light of thefirst color under the driving of the driving substrate 10; a first bandgap layer 30 disposed on the light emitting unit 21, the second lightemitting unit 22, and the third light emitting unit 23, and configuredto transmit the light of the first color and reflect the light of thesecond color and the light of the third color in the light exitdirection; a second conversion unit 42 and a third color conversion unit43 disposed on the first band gap layer 30; the second color conversionunit 42 corresponding to the position of the second light emitting unit22 and being configured to convert the light of the first color emittedfrom the second light emitting unit 22 into the light of the secondcolor; the third color conversion unit 43 corresponding to the positionof the third light emitting unit 23 and being configured to convert thelight of the first color emitted from the third light emitting unit 23into the light of the third color; a planarization layer 50 covering thefirst band gap layer 30, the second color conversion unit 42 and thethird color conversion unit 43; a color filter layer including a secondfilter unit 62 and a third filter unit 63 provided on the planarizationlayer 50, the second filter unit 62 corresponding to the position of thesecond color conversion unit 42 and being configured to transmit thelight of the second color in the light exit direction and absorb thelight of the first color; the third filter unit 63 corresponding to theposition of the third color conversion unit 43 and being configured totransmit the light of the third color in the light exit direction andabsorb the light of the first color. In this embodiment, the colorfilter (CF) layer may be made of an organic material. The composition,structure, and preparation of the color filter layer are well known tothose skilled in the art, and will not be repeated here.

This embodiment can achieve the technical effects of the embodimentsshown in FIGS. 1a to 1c , including improving the light output and lightoutput efficiency of the light of the second color and the light of thethird color, and improving the color purity of the light of the secondcolor and the light of the third color. In the embodiment shown in FIGS.1a to 1c , the light of the first color cannot be completely convertedby the second color conversion unit 42 and the third color conversionunit 43. The light of the second color emitted from the second colorconversion unit 42 and the light of the third color emitted from thethird color conversion unit 43 may contain unconverted light of thefirst color. Therefore, in this embodiment, the second filter unit 62and the third filter unit 63 are provided on the light exit path of thesecond color conversion unit 42 and the third color conversion unit 43to absorb unconverted light of the first color, further improving thecolor purity of the light of the second color and the light of the thirdcolor. In addition, by providing the color filter layer in thisembodiment, it is also possible to effectively reduce the incidence ofexternal light on the color conversion layer and reduce the interferenceof external light.

Table 1 shows the comparison test results of the brightness of the lightemitted from an embodiment of the present disclosure and a comparativeexample. In Table 1, R represents red light, G represents green light, Brepresents blue light, Brightness represents brightness of the light,CIEx and CIEy represent CIE color space coordinates, and DCI-P3 colorgamut is a parameter that describes the color richness of the display.Item 1 is a comparative example using a quantum dot conversion layer QDsand a color filter layer CF. Item 2 is an embodiment of the presentdisclosure using a first band gap layer PBG1, a quantum dot conversionlayer QDs, and a color filter layer CF. The structure of the comparativeexample is different from the structure of the embodiment of the presentdisclosure in that the first band gap layer is not provided in thestructure of the comparative example. As shown in Table 1, under thecondition that the amount of blue light emitted from the three lightemitting units is constant, the brightness of the three colors of thecomparative example is set to 100%. The brightness of the output redlight R of the embodiment of the present disclosure is 135%, thebrightness of the output green light G of the embodiment of the presentdisclosure is 133%, which are greater than those of the comparativeexample. Meanwhile, the CIE color space coordinates and DCI-P3 colorgamut of the red, green and blue light of the embodiment of the presentdisclosure are similar to the comparative example. The reason for theslight decrease in the brightness of the output blue light in theembodiment of the present disclosure is that the first band gap layer isprovided, and the first band gap layer cannot yet realize 100%transmission for blue light. In view of this, in actual implementation,the first band gap layer may not be provided at the positioncorresponding to the first light emitting unit, and the first band gaplayer is only provided at the position corresponding to the second lightemitting unit and the third light emitting unit. The comparison testresults show that the embodiment of the present disclosure effectivelyimproves the light output and the light output efficiency of red lightand green light.

TABLE 1 the brightness of output light of the embodiment of the presentdisclosure and comparative example DCI-P3 R G B color Item Structuralfeatures Brightness CIEx CIEy Brightness CIEx CIEy Brightness CIEx CIEygamut 1  QDs + CF 100% 0.706 0.293 100% 0.203 0.757 100% 0.145 0.035100% 2 PBG1 + QDs + CF 135% 0.706 0.293 133% 0.203 0.757  81% 0.1460.031 100%

Similarly, on the basis of the embodiment shown in FIG. 5, the OLEDdisplay substrate of the embodiment of the present disclosure can bemodified in various ways. For example, a first filter unit 61 may alsobe provided. The position of the first filter unit 61 corresponds to theposition of the first light emitting unit 21, and the first filter unit61 is configured to transmit the light of the first color in the lightexit direction and improve the color purity of the light of the firstcolor.

FIG. 6 is a schematic structural diagram of yet another embodiment of anOLED display substrate provided by the present disclosure. Theembodiment of the present disclosure is another modification of theembodiment shown in FIG. 1b (since the first color conversion unit isoptional, the first color conversion unit 41 in FIG. 1b is omitted inFIG. 6), A second band gap layer is also provided in the embodiment ofthe present disclosure. As shown in FIG. 6, the OLED display substrateof the embodiment of the present disclosure includes: a drivingsubstrate 10; a first light emitting unit 21, a second light emittingunit 22, and a third light emitting unit 23 periodically arranged on thedriving substrate 10; the light emitting unit 21, the second lightemitting unit 22, and the third light emitting unit 23 being capable ofemitting light of the first color under the driving of the drivingsubstrate 10; a first band gap layer 30 disposed on the light emittingunit 21, the second light emitting unit 22, and the third light emittingunit 23, and configured to transmit the light of the first color andreflect the light of the second color and the light of the third colorin the light exit direction; a second conversion unit 42 and a thirdcolor conversion unit 43 disposed on the first band gap layer 30; thesecond color conversion unit 42 corresponding to the position of thesecond light emitting unit 22 and being configured to convert the lightof the first color emitted from the second light emitting unit 22 intothe light of the second color; the third color conversion unit 43corresponding to the position of the third light emitting unit 23 andbeing configured to convert the light of the first color emitted fromthe third light emitting unit 23 into the light of the third color; aplanarization layer 50 covering the first band gap layer 30, the secondcolor conversion unit 42 and the third color conversion unit 43; asecond band gap layer disposed on the planarization layer 50, the secondband gap layer including at least a second band gap unit 72 and a thirdband gap unit 73; the second band gap unit 72 corresponding to theposition of the second color conversion unit 42, the second band gapunit 72 being configured to transmit the light of the second color inthe light exit direction and reflect the light of the first color in thedirection opposite to the light exit direction; the third band gap unit73 corresponding to the position of the third color conversion unit 43,the third band gap unit 73 being configured to transmit the light of thethird color in the light exit direction and reflect the light of thefirst color in the direction opposite to the light exit direction.

In this embodiment, each of the second band gap unit 72 and the thirdband gap unit 73 may be a photonic band gap PBG layer/electromagneticband gap EBG layer, or a stacked structure layer. The structure,reflection principle, etc. of the second band gap unit 72 and the thirdband gap unit 73 are substantially the same to those of the first bandgap layer in the embodiments shown in FIGS. 1a to 1c . The second bandgap unit 72 has a transmittance of ≥80% for light of the second colorand a reflectivity of ≥85% for light of the first color. Optionally, thesecond band gap unit 72 has a transmittance of ≥90% for light of thesecond color. Optionally, the second band gap unit 72 has a reflectivityof ≥95% for the light of the first color. The third band gap unit 73 hasa transmittance of ≥80% for the light of the third color and areflectivity of ≥85% for the light of the first color. Optionally, thethird band gap unit 73 has a transmittance of ≥90% for the light of thethird color. Optionally, the third band gap unit 73 has a reflectivityof ≥95% for the light of the first color.

This embodiment can achieve the technical effects of the embodimentsshown in FIGS. 1a to 1c , including improving the light output and lightoutput efficiency of the light of the second color and the light of thethird color, and improving the color purity of the light of the secondcolor and the light of the third color. In the embodiment shown in FIGS.1a to 1c , the light of the first color cannot be completely convertedby the second color conversion unit 42 and the third color conversionunit 43. The light of the second color emitted from the second colorconversion unit 42 and the light of the third color emitted from thethird color conversion unit 43 may contain unconverted light of thefirst color. Therefore, in this embodiment, the second band gap unit 72and the third band gap unit 73 are provided on the light exit path ofthe second color conversion unit 42 and the third color conversion unit43, thereby reflecting unconverted light of the first color to the colorconversion layer and converting light of the first color again, furtherimproving the light output and light output efficiency of the light ofthe second color and the light of the third color, and improving thecolor purity of the light of the second color and the light of the thirdcolor. In addition, by providing the second band gap layer in thisembodiment, it is also possible to effectively reduce the incidence ofexternal light on the color conversion layer and reduce the interferenceof external light.

FIG. 7 is a working principle diagram of the second band gap layer ofthe embodiment shown in FIG. 6 provided by the present disclosure. Asshown in FIG. 7, the working principle of the light emitting unit layer,the first band gap layer, and the color conversion layer are the same asthe embodiment in FIG. 1 (as shown in FIG. 4), and details are notrepeated here. Due to the limitation of the quantum dot material, afterthe light of the first color transmitted through the first band gaplayer 30 enters the second color conversion unit 42 and the third colorconversion unit 43, a small amount of the light of the first color willnot be converted into light of the second color and light of the thirdcolor. A part of this small amount of light of the first color may exitfrom the light exit surfaces of the second color conversion unit 42 andthe third color conversion unit 43, and enter the second band gap unit72 and the third band gap unit 73. Since the second band gap unit 72 andthe third band gap unit 73 has a high transmittance for light of thefirst color, the second band gap unit 72 and the third band gap unit 73reflect this part of light of the first color back to the second colorconversion unit 42 and the third color conversion unit 43 and conversionis performed again. In this way, the second band gap unit 72 and thethird band gap unit 73 reflect the light of the first color, theunconverted light of the first color can be continuously converted untilthe light of the first color is completely converted into the light ofthe second color and the light of the third color. The conversionefficiency is maximized, the light of the first color mixed in both thelight of the second color and the light of the third color is minimized,and the light output and the light output efficiency of the light of thesecond color and the light of the third color are maximized. The colorpurity is also maximized.

The color filter layer in the embodiment shown in FIG. 5 absorbs theunconverted blue light, and the second band gap layer in this embodimentreflects the unconverted blue light back to the color conversion unitfor conversion again. Compared with the embodiment shown in FIG. 5, thisembodiment has higher conversion efficiency, higher light output andlight output efficiency, and higher color purity.

Similarly, on the basis of the solutions of the embodiments shown inFIGS. 1a-1c , the OLED display substrate of this embodiment can bemodified in various ways. For example, a first band gap unit 71 may alsobe provided. The position of the first band gap unit 71 corresponds tothe position of the first light emitting unit 21, and the first band gapunit 71 is configured to transmit the light of the first color in thelight exit direction and improve the color purity of the light of thefirst color.

Table 2 shows the comparison test results of the output light brightnessof the embodiment of the present disclosure and the comparative example.In Table 2, the meanings of R, G, B, Brightness, CIEx, CIEy, and DCI-P3color gamut are the same as those in Table 1 above. Item 1 is acomparative example, using a quantum dot conversion layer QDs and acolor filter layer CF. Item 2 is the embodiment shown in FIG. 5, whichuses the first band gap layer PBG1, the quantum dot conversion layerQDs, and the color filter layer CF. Item 3 is the present embodiment,using the first band gap layer PBG1, the quantum dot conversion layerQDs, and the second band gap layer PBG2. As shown in Table 2, under thecondition that the amount of blue light emitted from the three lightemitting units is constant, the brightness of the three colors in thecomparative example is set to 100%. The brightness of the output redlight R in the embodiment shown in FIG. 5 is 135%, while the brightnessof the output red light R of the present embodiment is 179%; thebrightness of the output green light of the embodiment shown in FIG. 5is 133%, and the brightness of the output green light of the presentembodiment is 209%. Both the brightness of the output red light and thebrightness of the output green light are significantly larger than thoseof the embodiment shown in FIG. 5. For blue light B, the brightness ofthe output blue light of the embodiment shown in FIG. 5 is 81%, whilethe brightness of the output blue light of the present embodiment is220%. Meanwhile, the CIE color space coordinates and DCI-P3 color gamutof the red, green and blue light of the present embodiment are similarto the comparative example. The comparison test results show that thisembodiment not only effectively improves the light output and outputefficiency of red and green light, but also effectively improves theconversion efficiency. Without substantially reducing the color purityand color gamut of blue light, the second band gap layer effectivelyimproves the brightness of blue light.

TABLE 2 the brightness of output light of the embodiment of the presentdisclosure and comparative example DCI-P3 R G B color Item Structuralfeatures Brightness CIEx CIEy Brightness CIEx CIEy Brightness CIEx CIEygamut 1  QDs + CF 100% 0.706 0.293 100% 0.203 0.757 100% 0.145 0.035100% 2 PBG1 + QDs + CF 135% 0.706 0.293 133% 0.203 0.757  81% 0.1460.031 100% 3 PBG1 + QDs + PBG2 179% 0.681 0.301 209% 0.223 0.667 220%0.144 0.047  90%

FIGS. 8a, 8b, and 8c are spectrum diagrams of the embodiment shown inFIG. 6 provided by the present disclosure. In each figure, the lowerpart illustrates the light emitted from the light emitting unit layerand the color conversion layer, the middle part illustrates thetransmitted light and reflected light of the first band gap layer, andthe upper part illustrates the comparison of the transmitted light andthe reflected light between the color filter layer (the embodiment shownin FIG. 5) and the second band gap layer (this embodiment). The solidline is the transmittance, and the dotted line is the reflectivity.B-CF, G-CF, and R-CF respectively represent the blue filter layer, thegreen filter layer, and the red filter layer. B-PBG, G-PBG and R-PBGrepresent the first band gap unit (blue light), the second band gap unit(green light) and the third band gap unit (red light), respectively.B-OLED means blue light emitted from the light emitting unit. G-QD andR-QD represent green light and red light converted by the colorconversion unit, respectively. As shown in FIGS. 8a, 8b, and 8c , thefirst band gap layer has a higher transmittance for blue light and ahigher reflectivity for green and red light. The first band gap unit hasa higher transmittance for blue light, and the bandwidth of the emittedblue light is greater than that of the blue filter layer. The secondband gap unit has a higher transmittance for green light and a higherreflectivity for blue light, and the bandwidth of emitted green light isgreater than that of the green filter layer. The third band gap unit hasa higher transmittance for red light and a higher reflectivity for bluelight, and the bandwidth of the emitted red light is greater than thatof the red filter layer.

FIG. 9 is a schematic structural diagram of still another embodiment ofan OLED display substrate provided by the present disclosure. Thisembodiment is a modification of the embodiment shown in FIG. 6.Different from the embodiment shown in FIG. 6, this embodiment onlyprovides the second band gap layer and the first band gap layer is notprovided. As shown in FIG. 9, the OLED display substrate of thisembodiment includes: a driving substrate 10; a first light emitting unit21, a second light emitting unit 22, and a third light emitting unit 23periodically arranged on the driving substrate 10; the first lightemitting unit 21, the second light emitting unit 22, and the third lightemitting unit 23 being capable of emitting light of the first colorunder the driving of the driving substrate 10; a protective layer 80provided on the first light emitting unit 21, the second light emittingunit 22, and the third light emitting unit 23; a second color conversionunit 42 and a third color conversion unit 43 provided on the protectivelayer 80, the second color conversion unit 42 corresponding to theposition of the second light emitting unit 22 and being configured toconvert the light of the first color emitted from the second lightemitting unit 22 into the light of the second color; the third colorconversion unit 43 corresponding to the position of the third lightemitting unit 23 and being configured to convert the light of the firstcolor emitted from the third light emitting unit 23 into the light ofthe third color; a planarization layer 50 covering the protective layer80, the second color conversion unit 42 and the third color conversionunit 43; a second band gap layer disposed on the planarization layer 50,the second band gap layer including at least a second band gap unit 72and a third band gap unit 73; the second band gap unit 72 correspondingto the position of the second color conversion unit 42, the second bandgap unit 72 being configured to transmit the light of the second colorin the light exit direction and reflect the light of the first color inthe direction opposite to the light exit direction; the third band gapunit 73 corresponding to the position of the third color conversion unit43, the third band gap unit 73 being configured to transmit the light ofthe third color in the light exit direction and reflect the light of thefirst color in the direction opposite to the light exit direction.

Similar to the embodiment shown in FIG. 6, in this embodiment, each ofthe second band gap unit 72 and the third band gap unit 73 may be aphotonic band gap PBG layer/electromagnetic band gap EBG layer, or astacked structure layer. The second band gap unit 72 has a transmittanceof ≥80% for light of the second color and a reflectivity of ≥85% forlight of the first color. Optionally, the second band gap unit 72 has atransmittance of ≥90% for light of the second color. Optionally, thesecond band gap unit 72 has a reflectivity of ≥95% for the light of thefirst color. The third band gap unit 73 has a transmittance of ≥80% forthe light of the third color and a reflectivity of ≥85% for the light ofthe first color. Optionally, the third band gap unit 73 has atransmittance of ≥90% for the light of the third color. Optionally, thethird band gap unit 73 has a reflectivity of ≥95% for the light of thefirst color.

Although the first band gap layer is not provided in this embodiment,the second color conversion unit 42 and the third color conversion unithaving band gap characteristics are provided in this embodiment. Whenthe unconverted light of the first color from the second colorconversion unit 42 and the third color conversion unit 43 is incident onthe second band gap unit 72 and the third band gap unit 73, since thesecond band gap unit 72 and the third band gap unit 73 have the highreflectivity for the light of the first color, this part of the light ofthe first color is reflected back to the second color conversion unit 42and the third color conversion unit 43 by the second band gap unit 72and the third band gap unit 73, and is converted again. In this way, thesecond band gap unit 72 and the third band gap unit 73 reflect the lightof the first color, and the unconverted light of the first color can becontinuously converted until all conversions are completed, which alsoimproves the conversion efficiency and reduces the light of the firstcolor in the light of the second color and the light of the third color,improving the light output and light output efficiency of the light ofthe second color and the light of the third color, and improving thecolor purity of the light of the second color and the light of the thirdcolor.

Table 3 shows the comparison test results of the output light brightnessof the embodiment of the present disclosure and the comparative example.In Table 3, the meanings of R, G, B, Brightness, CIEx, CIEy, and DCI-P3color gamut are the same as those in Table 1 above. Item 1 is acomparative example, using a quantum dot conversion layer QDs and acolor filter layer CF. Item 4 is the present embodiment, which uses thequantum dot conversion layer QDs and the second band gap layer PBG2. Asshown in Table 3, under the condition that the amount of blue lightemitted from the three light emitting units is constant, the brightnessof the three colors of the comparative example is set to 100%. Thebrightness of the output red light R of the present embodiment is 132%,the brightness of the output green light G of the present embodiment is157%, the brightness of the output blue light B of the presentembodiment is 220%, which are all greater than those of the comparativeexample. Meanwhile, the CIE color space coordinates and DCI-P3 colorgamut of the red, green and blue light of the present embodiment aresimilar to the comparative example. The comparison test result showsthat, compared with the existing structure provided with the colorfilter layer, this embodiment effectively improves the light output andthe light output efficiency of red light and green light. In addition,as can be seen from the comparison between Table 2 and Table 3, althoughthe brightness of the output red and green light of this embodiment islower than the solution of the embodiment shown in FIG. 6, thisembodiment has the advantages of simple structure and less preparationprocess, it can thus be used when the brightness requirements are met.

TABLE 3 the brightness of output light of the embodiment of the presentdisclosure and comparative example DCI-P3 R G B color Item Structuralfeatures Brightness CIEx CIEy Brightness CIEx CIEy Brightness CIEx CIEygamut 1 QDs + CF 100% 0.706 0.293 100% 0.203 0.757 100% 0.145 0.035 100%4 QDs + PBG2 132% 0.681 0.301 157% 0.223 0.667 220% 0.144 0.047  90%

The foregoing embodiments have been described by taking the example thatthe first band gap layer, the color conversion unit, the color filterlayer/the second band gap layer are all provided on the drivingsubstrate. Based on the technical solutions of the foregoingembodiments, the OLED display substrate may further include a coverplate. The light emitting units may be provided on the driving substrateto form a light emitting substrate. The first band gap layer, the colorconversion unit, the color filter layer/the second band gap layer may beprovided on the cover plate to form a light processing substrate. Then,an alignment process may be performed on the light emitting substrateand the light processing substrate to form an OLED display substrate.When the band gap layer and the color conversion unit are arranged onthe cover plate, the influence of the process of preparing the band gaplayer and the color conversion unit on the light emitting unit layerdoes not need to be considered, and there is a wide space for selectingmaterials and process parameters.

Based on the technical concept of the foregoing embodiments, anembodiment of the present disclosure also provides a method formanufacturing an OLED display substrate. The method for manufacturingthe OLED display substrate includes: S1, forming a light emitting unitlayer that emits light of a first color; and S2, forming a band gaplayer and a color conversion layer, the color conversion layer beingconfigured to convert a part of the light of the first color into lightof a second color and light of a third color, respectively; the band gaplayer being configured to transmit the light of the second color and thelight of the third color in a light exit direction of the OLED displaysubstrate.

In one embodiment, step S1 includes: forming a first light emittingunit, a second light emitting unit, and a third light emitting unit on adriving substrate, which are periodically arranged and emit light of thefirst color. Step S2 includes: forming a first band gap layer on thelight emitting unit layer, the first band gap layer being configured totransmit the light of the first color in the light exit direction andreflect the light of the second color and the light of the third color;forming a color conversion layer including a second color conversionunit and a third color conversion unit on the first band gap layer, thesecond color conversion unit corresponding to the position of the secondlight emitting unit and being configured to convert the light of thefirst color into light of the second color, the third color conversionunit corresponding to the position of the third light emitting unit andbeing configured to convert the light of the first color into light ofthe third color.

The method may further include: forming a planarization layer coveringthe color conversion layer; and forming a color filter layer including asecond filter unit and a third filter unit on the planarization layer.The second filter unit corresponds to the position of the second colorconversion unit, and is configured to transmit the light of the secondcolor in the light exit direction and absorb the light of the firstcolor. The third filter unit corresponds to the position of the thirdcolor conversion unit, and is configured to transmit the light of thethird color in the light exit direction and absorb the light of thefirst color.

The method may further include: forming a planarization layer coveringthe color conversion layer; and forming a second band gap layerincluding a second band gap unit and a third band gap unit on theplanarization layer. The second band gap unit corresponds to theposition of the second color conversion unit, and is configured totransmit the light of the second color in the light exit direction andreflect the light of the first color in a direction opposite to thelight exit direction. The third band gap unit corresponds to theposition of the third color conversion unit, and is configured totransmit the light of the third color in the light exit direction andreflect the light of the first color in the direction opposite to thelight exit direction.

In another embodiment, step S1 includes: forming a first light emittingunit, a second light emitting unit, and a third light emitting unit onthe driving substrate, which are periodically arranged and emit light ofa first color. Step S2 includes: forming a protective layer covering thelight emitting unit layer; forming a color conversion layer including asecond color conversion unit and a third color conversion unit on theprotective layer. The second color conversion unit corresponds to theposition of the second light emitting unit, and is configured to convertthe light of the first color into light of a second color. The thirdcolor conversion unit corresponds to the position of the third lightemitting unit, and is configured to convert the light of the first colorinto light of a third color. A planarization layer covering the colorconversion layer is formed. A second band gap layer including a secondband gap unit and a third band gap unit is formed on the planarizationlayer. The second band gap unit corresponds to the position of thesecond color conversion unit, and is configured to transmit the light ofthe second color in the light exit direction and reflect the light ofthe first color in a direction opposite to the light exit direction. Thethird band gap unit corresponds to the position of the third colorconversion unit, and is configured to transmit the light of the thirdcolor in the light exit direction and reflect the light of the firstcolor in the direction opposite to the light exit direction.

In yet another embodiment, step S1 includes: forming a first lightemitting unit, a second light emitting unit, and a third light emittingunit on a driving substrate to form a light emitting substrate. Thefirst light emitting unit, the second light emitting unit, and the thirdlight emitting unit are periodically arranged and emit light of thefirst color. Step S2 includes: forming a band gap layer and a colorconversion layer on a cover plate to form a light processing substrate.

The method may further include: performing an alignment process on thelight emitting substrate and the light processing substrate.

The first band gap layer 30 has a transmittance of ≥80% for light of thefirst color, and a reflectivity of ≥85% for light of the second colorand light of the third color. Optionally, the first band gap layer 30has a transmittance of ≥90% for the light of the first color.Optionally, the first band gap layer 30 has a reflectivity of ≥95% forthe light of the second color and the light of the third color. Thesecond band gap unit 72 has a transmittance of ≥80% for light of thesecond color and a reflectivity of ≥85% for the light of the firstcolor. Optionally, the second band gap unit 72 has a transmittance of≥90% for the light of the second color. Optionally, the second band gapunit 72 has a reflectivity of ≥95% for the light of the first color. Thethird band gap unit 73 has a transmittance of 80% for the light of thethird color and a reflectivity of ≥85% for the light of the first color.Optionally, the third band gap unit 73 has a transmittance of ≥90% forthe light of the third color. Optionally, the third band gap unit 73 hasa reflectivity of ≥95% for the light of the first color.

The first band gap layer and the second band gap layer are photonic bandgap layers or stacked structure layers. The thickness of the photonicband gap layer is 0.5 μm to 2.0 μm, and the thickness of the stackedstructure layer is 0.5 μm to 10.0 μm. The stacked structure layerincludes 3 to 5 dielectric layers stacked in sequence, and adjacentdielectric layers have different refractive indexes.

The light of the first color is blue light, and the color conversionlayer is a quantum dot conversion layer.

The structures, materials, and related parameters of the light emittingunit layer, the color conversion layer, the first band gap layer, andthe second band gap layer have been described in detail in the foregoingembodiments, and will not be repeated here.

When forming the light emitting unit layer, an organic light emittinglayer covering the entire driving substrate may be formed on the drivingsubstrate by using an evaporation process without using FMM. Whenforming the second color conversion unit or the third color conversionunit, a photoresist doped with quantum dots of the second color or thethird color may be used by spin coating, and then a photolithographyprocess may be performed; it is also possible to use glue doped withquantum dots of the second color and glue doped with quantum dots of thethird color to perform inkjet printing respectively, or to use theimprint method. When forming the second filter unit and the third filterunit, vapor deposition, inkjet printing, or photolithography may beused. When forming the first band gap layer and the second band gaplayer, one or more methods of dielectric rod stacking, precisionmechanical drilling, colloidal particle self-organization growth,colloidal solution self-organization growth, and semiconductor processcan be used. The above process methods are all mature processes in theart and are well known to those skilled in the art, and will not berepeated here.

Based on the technical concept of the foregoing embodiments, anembodiment of the present disclosure also provides an OLED displaydevice including the OLED display substrate provided in any of theforegoing embodiments. The OLED display device may be any product orcomponent with a display function such as a display panel, a mobilephone, a tablet computer, a television, a notebook computer, a digitalphoto frame, a navigator, and the like.

Of course, implementing any of the products or methods of the presentdisclosure does not necessarily need to achieve all the advantagesdescribed above at the same time. The objects and advantages of theembodiments of the present disclosure can be realized and obtained bythe structures particularly pointed out in the specification, claims,and drawings.

In the description of the embodiments of the present disclosure, itshould be understood that the terms “first”, “second”, and “third” arefor descriptive purposes only, and cannot be understood as indicating orimplying relative importance or implicitly indicating that the order ornumber of technical features indicated.

In the description of the embodiments of the present disclosure, itshould be understood that the terms “middle”, “upper”, “lower”, “front”,“back”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”,etc. indicating the orientation or positional relationship are based onthe orientation or positional relationship shown in the drawings, justto facilitate the description of the present disclosure and simplify thedescription, and does not indicate or imply that the device or elementreferred to must have a specific orientation, or be constructed andoperated in a specific orientation, and therefore cannot be construed asa limitation of the present disclosure.

In the description of the embodiments of the present disclosure, itshould be noted that, unless otherwise clearly specified and limited,the terms “installation”, “connection”, and “connected” should beunderstood in a broad sense, for example, it can be a fixed connection,a detachable connection, or an integral connection; it can be amechanical connection or an electrical connection; it can be a directconnection or an indirect connection through an intermediate medium, orit can be an internal connection between two components. For those ofordinary skill in the art, the specific meaning of the above terms inthe present disclosure may be understood in specific situations.

Although the embodiments disclosed in the present disclosure are asdescribed above, the described contents are only the embodiments adoptedto facilitate understanding of the present disclosure, and are notintended to limit the present disclosure. Any person skilled in the artto which this disclosure belongs can make any modifications and changesin the form and details of implementation without departing from thespirit and scope disclosed in this disclosure. The patent protectionscope of this disclosure is defined by the appended claims.

1. An organic light emitting diode display substrate, comprising: alight emitting unit layer; a first band gap layer; and a colorconversion layer, wherein the first band gap layer and the colorconversion layer are on a light exit path of the light emitting unitlayer, wherein the light emitting unit layer comprises a first lightemitting unit, a second light emitting unit, and a third light emittingunit periodically arranged on a driving substrate and configured to emitlight of a first color, wherein the color conversion layer is configuredto convert a part of the light of the first color into light of a secondcolor and light of a third color, respectively, wherein the first bandgap layer is between the light emitting unit layer and the colorconversion layer and overlaps the second light emitting unit and thethird light emitting unit, and wherein the first band gap layer isconfigured to transmit the light of the first color in a light exitdirection, and reflect the light of the second color and the light ofthe third color.
 2. The organic light emitting diode display substrateaccording to claim 1, wherein the color conversion layer comprises asecond color conversion unit on a light exit path of the second lightemitting unit and is configured to convert the light of the first colorinto the light of the second color, and a third color conversion unit ona light exit path of the third light emitting unit and is configured toconvert the light of the first color into the light of the third color.3. The organic light emitting diode display substrate according to claim1, wherein the first band gap layer further overlaps the first lightemitting unit.
 4. The organic light emitting diode display substrateaccording to claim 2, further comprising: a color filter layer on alight exit path of the second color conversion unit and the third colorconversion unit, wherein the color filter layer is configured totransmit the light of the second color and the light of the third colorin the light exit direction and absorb the light of the first color. 5.The organic light emitting diode display substrate according to claim 4,wherein the color filter layer comprises a second filter unit and athird filter unit, wherein the second filter unit corresponds to aposition of the second color conversion unit, and is configured totransmit the light of the second color in the light exit direction andabsorb the light of the first color, and wherein the third filter unitcorresponds to a position of the third color conversion unit, and isconfigured to transmit the light of the third color in the light exitdirection and absorb the light of the first color.
 6. The organic lightemitting diode display substrate according to claim 1, wherein the firstband gap layer has a transmittance of ≥80% for the light of the firstcolor, and has a reflectivity of ≥85% for the light of the second colorand the light of the third color.
 7. The organic light emitting diodedisplay substrate according to claim 2, further comprising: a secondband gap layer on a light exit path of the second color conversion unitand the third color conversion unit, wherein the second band gap layeris configured to transmit the light of the second color and the light ofthe third color in the light exit direction and reflect the light of thefirst color in a direction opposite to the light exit direction.
 8. Theorganic light emitting diode display substrate according to claim 7,wherein the second band gap layer is on a planarization layer on thesecond color conversion unit and the third color conversion unit, andcomprises a second band gap unit and a third band gap unit, wherein thesecond band gap unit corresponds to a position of the second colorconversion unit, and is configured to transmit the light of the secondcolor in the light exit direction and reflect the light of the firstcolor in the direction opposite to the light exit direction, wherein thethird band gap unit corresponds to a position of the third colorconversion unit, and is configured to transmit the light of the thirdcolor in the light exit direction and reflect the light of the firstcolor in the direction opposite to the light exit direction.
 9. Theorganic light emitting diode display substrate according to claim 8,wherein the second band gap unit has a transmittance of ≥80% for thelight of the second color and a reflectivity of ≥85% for the light ofthe first color, wherein the third band gap unit has a transmittance of≥80% for the light of the third color and a reflectivity of ≥85% for thelight of the first color.
 10. The organic light emitting diode displaysubstrate according to claim 7, wherein each of the first band gap layerand the second band gap layer is one of a photonic band gap layer or astacked structure layer, wherein a thickness of the photonic band gaplayer is 0.5 μm to 2.0 μm, wherein a thickness of the stacked structurelayer is 0.5 μm to 10.0 μm, wherein the stacked structure layercomprises 3 to 5 sequentially stacked dielectric layers, and whereinrefractive indexes of adjacent dielectric layers of the sequentiallystacked dielectric layers are different from each other.
 11. The organiclight emitting diode display substrate according to claim 1, wherein thelight of the first color comprises blue light, and wherein the colorconversion layer comprises a quantum dot conversion layer.
 12. Anorganic light emitting diode display substrate, comprising: a lightemitting unit layer; a color conversion layer; and a second band gaplayer, wherein the color conversion layer and the second band gap layerare on a light exit path of the light emitting unit layer, wherein thelight emitting unit layer comprises a first light emitting unit, asecond light emitting unit, and a third light emitting unit periodicallyarranged on a driving substrate and configured to emit light of a firstcolor, wherein the color conversion layer is configured to convert apart of the light of the first color into light of a second color andlight of a third color, respectively, wherein the second band gap layeris on a side of the color conversion layer away from the light emittingunit layer, wherein the second band gap layer is configured to transmitthe light of the second color and the light of the third color in alight exit direction, and reflect the light of the first color in adirection opposite to the light exit direction.
 13. The organic lightemitting diode display substrate according to claim 12, wherein thecolor conversion layer comprises a second color conversion unit on alight exit path of the second light emitting unit and is configured toconvert the light of the first color into the light of the second color,and wherein a third color conversion unit on a light exit path of thethird light emitting unit is configured to convert the light of thefirst color into the light of the third color.
 14. The organic lightemitting diode display substrate according to claim 13, wherein thesecond band gap layer is on a planarization layer on the second colorconversion unit and the third color conversion unit, and comprises asecond band gap unit and a third band gap unit, wherein the second bandgap unit corresponds to a position of the second color conversion unit,and is configured to transmit the light of the second color in the lightexit direction and reflect the light of the first color in a directionopposite to the light exit direction, wherein the third band gap unitcorresponds to a position of the third color conversion unit, and isconfigured to transmit the light of the third color in the light exitdirection and reflect the light of the first color in the directionopposite to the light exit direction, wherein the second band gap unithas a transmittance of ≥80% for the light of the second color and areflectivity of ≥85% for the light of the first color, and wherein thethird band gap unit has a transmittance of ≥80% for the light of thethird color and a reflectivity of ≥85% for the light of the first color.15. The organic light emitting diode display substrate according toclaim 12, wherein the second band gap layer is one of a photonic bandgap layer or a stacked structure layer, wherein a thickness of thephotonic band gap layer is 0.5 μm to 2.0 μm, wherein a thickness of thestacked structure layer is 0.5 μm to 10.0 μm, wherein the stackedstructure layer comprises 3 to 5 sequentially stacked dielectric layers,and wherein refractive indexes of adjacent dielectric layers of thesequentially stacked dielectric layers are different from each other.16. The organic light emitting diode display substrate according toclaim 12, wherein the light of the first color comprises blue light, andwherein the color conversion layer comprises a quantum dot conversionlayer.
 17. A display device comprising the organic light emitting diodedisplay substrate according to claim
 1. 18. A method for manufacturingthe organic light emitting diode display substrate, comprising: forminga light emitting unit layer that is configured to emit light of a firstcolor, the light emitting unit layer comprising a first light emittingunit, a second light emitting unit, and a third light emitting unitperiodically arranged on a driving substrate; and forming a first bandgap layer and a color conversion layer, wherein the first band gap layeris between the light emitting unit layer and the color conversion layer,wherein the color conversion layer is configured to convert a part ofthe light of the first color into light of a second color and light of athird color, respectively, and wherein the first band gap layer isconfigured to transmit the light of the first color in a light exitdirection, and reflect the light of the second color and the light ofthe third color.
 19. The method according to claim 18, furthercomprising: forming a second band gap layer, wherein the second band gaplayer is on a side of the color conversion layer away from the lightemitting unit layer, and wherein the second band gap layer is configuredto transmit the light of the second color and the light of the thirdcolor in the light exit direction and reflect the light of the firstcolor in a direction opposite to the light exit direction.
 20. A methodfor manufacturing the organic light emitting diode display substrateaccording to claim 12, comprising: forming the light emitting unit layerthat is configured to emit light of the first color; and forming thecolor conversion layer and the second band gap layer